Clefts of the lip and palate often result in significant nasal deformities which tend to reduce the size of the nasal airway. Similarly, surgical procedures to correct nasal asymmetry, palatal incompetency or maxillary deficits can also impair nasal breathing. A number of clinicians have suggested that impairment of nasorespiratory function influences dentofacial growth; others disagree. The controversy stems from our inability to define airway impairment quantitatively and assess mouthbreathing objectively. In cleft palate, the emphasis has been on esthetics and speech with little concern for airway patency in spite of the fact that treatment can compromise the upper airway. The specific aims of this research are to use newly developed quantitative techniques to: 1. determine how the nasal airway of cleft lip/palate individuals differs from normals, 2. evaluate the effects of physical management on the cleft nasal airway, 3. assess the effects of cleft lip/palate on nasal and oral breathing, 4. define nasal airway impairment in children, and 5. determine how the respiratory system responds to airway impairment. Recent advances in respiratory technology provide the opportunity to quantitatively assess breathing in this group of patients. Such information could be critical for decisions relating to physical management. One approach will be to measure nasal airway size using a technique developed by Warren for speech research. The other technique is a non-invasive method for measuring oral-nasal respiration. Finally, body plethysmography will be used to measure airway resistance throughout the respiratory tract. This research represents a new direction in the objective quantification of upper airway breathing and airway impairment in the cleft and normal populations. The results are expected to provide needed information concerning the immediate and long-term effects of physical management. Since impairment has been implicated as contributing to growth disturbances, it is especially important to determine the extent of this in a population which already demonstrates tissue deficiencies, distortions, and displacement problems. Additionally, these studies concern breathing as a regulating system phenomenon, an area that appears promising in terms of understanding how the body responds both morphologically and physiologically to airway impairment.